1. Field of the Invention
The present invention relates to a communication system having a first communication apparatus capable of communication via a first communication line and a second communication apparatus capable of communication via a second communication line, and to communication apparatus used for the system.
2. Related Background Art
Wireless portable telephones and personal handy-phone system (PHS) telephones are greatly prevailing nowadays, and some people have telephones more than one. A user can hold a wireless telephone in hand and can make a telephone conversation anywhere and anytime. It is a great convenience for a user to have such a telephone.
Many telephones have no hands-free function for hands-free talking. Even if a wireless portable telephone or PHS telephone is provided with the hands-free function, the sound quality is not good because a small speaker and a small microphone built in the telephone are used.
The distribution of facsimile apparatus, which are typical communication apparatus connectable to a public telephone line, is very high. The future use of a facsimile apparatus is considered not to be lowered, because an original image or text can be easily transmitted or received.
Household telephones are being increasingly replaced by facsimile apparatus which are provided with a hands-free talking function and an automatic answering telephone. Acoustic components used with a facsimile apparatus having the hands-free talking function have good characteristics. A dedicated echo canceler is also built in a facsimile apparatus.
A wireless portable telephone or PHS telephone used via a cell system base station is required to be compact and light in weight so as to facilitate to hold it outdoors.
It cannot always be said that a compact and light telephone is easy to use. Namely, a compact telephone uses a compact speaker so that the sound volume is small and the sound quality is poor, and the sensitivity of the microphone is low. Therefore, it is necessary to use the microphone and speaker set near at a user, and the so-called hands-free talking is difficult.
In addition, a small telephone has a small battery in order to reduce the weight of the telephone. If a large sound is reproduced or an echo canceler is driven for the hands-free talking, a large current flows and the battery is consumed greatly. A speech time or a standby time may be shortened. Such a telephone is not therefore suitable for indoor use.